1. Field
Example embodiments relate to a spectrum measuring apparatus. More particularly, example embodiments relate to a light focusing unit and a spectrum measuring apparatus having the same, capable of guiding polarized light to be incident on a sample at multiple incidence angles, and measuring both split-beam and arc-minute spectra of numerous wavelength bands at the incidence angles.
2. Description of Related Art
Semiconductor devices are fabricated by sequentially or selectively performing numerous unit processes, e.g., diffusion, deposition, ion implantation, exposure, cleaning, etc., on a substrate. For example, during fabrication of a semiconductor device, an ultra thin film having a thickness of several nanometers or less may be deposited on the substrate. A spectrum measuring apparatus, e.g., a spectroscopic ellipsometer, may be used to, e.g., precisely, measure the thickness of the ultra thin film and optical properties of a material of which the ultra thin film is formed.
The spectroscopic ellipsometer determines complex refractive indices n and k using a pair of spectra Δ and Ψ within an entire wavelength region measured at a single incidence angle. For example, as illustrated in FIG. 1, a conventional spectroscopic ellipsometer may include a light source section 10 emitting light, a polarized light generator 20 polarizing the light of the light source section 10 to cause the polarized light to be incident on a sample 1, a polarized light detecting section 30 detecting the polarized light reflected from the sample 1, and a detector 40 acquiring spectra from the detected polarized light. The spectroscopic ellipsometer may also include a compensator 21.
The conventional spectroscopic ellipsometer may be a single incidence-angle spectroscopic ellipsometer. However, the conventional single incidence-angle spectroscopic ellipsometer may have a low sensitivity to a vertical geometric structure of a thin film material, despite having a rapid measurement speed.